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<a href="channel__base_8hpp.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno">    1</span><span class="comment">/* Flow-IPC: Structured Transport</span></div>
<div class="line"><a id="l00002" name="l00002"></a><span class="lineno">    2</span><span class="comment"> * Copyright (c) 2023 Akamai Technologies, Inc.; and other contributors.</span></div>
<div class="line"><a id="l00003" name="l00003"></a><span class="lineno">    3</span><span class="comment"> * Each commit is copyright by its respective author or author&#39;s employer.</span></div>
<div class="line"><a id="l00004" name="l00004"></a><span class="lineno">    4</span><span class="comment"> *</span></div>
<div class="line"><a id="l00005" name="l00005"></a><span class="lineno">    5</span><span class="comment"> * Licensed under the MIT License:</span></div>
<div class="line"><a id="l00006" name="l00006"></a><span class="lineno">    6</span><span class="comment"> *</span></div>
<div class="line"><a id="l00007" name="l00007"></a><span class="lineno">    7</span><span class="comment"> * Permission is hereby granted, free of charge, to any person obtaining a copy</span></div>
<div class="line"><a id="l00008" name="l00008"></a><span class="lineno">    8</span><span class="comment"> * of this software and associated documentation files (the &quot;Software&quot;), to deal</span></div>
<div class="line"><a id="l00009" name="l00009"></a><span class="lineno">    9</span><span class="comment"> * in the Software without restriction, including without limitation the rights</span></div>
<div class="line"><a id="l00010" name="l00010"></a><span class="lineno">   10</span><span class="comment"> * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell</span></div>
<div class="line"><a id="l00011" name="l00011"></a><span class="lineno">   11</span><span class="comment"> * copies of the Software, and to permit persons to whom the Software is</span></div>
<div class="line"><a id="l00012" name="l00012"></a><span class="lineno">   12</span><span class="comment"> * furnished to do so, subject to the following conditions:</span></div>
<div class="line"><a id="l00013" name="l00013"></a><span class="lineno">   13</span><span class="comment"> *</span></div>
<div class="line"><a id="l00014" name="l00014"></a><span class="lineno">   14</span><span class="comment"> * The above copyright notice and this permission notice shall be included in</span></div>
<div class="line"><a id="l00015" name="l00015"></a><span class="lineno">   15</span><span class="comment"> * all copies or substantial portions of the Software.</span></div>
<div class="line"><a id="l00016" name="l00016"></a><span class="lineno">   16</span><span class="comment"> *</span></div>
<div class="line"><a id="l00017" name="l00017"></a><span class="lineno">   17</span><span class="comment"> * THE SOFTWARE IS PROVIDED &quot;AS IS&quot;, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR</span></div>
<div class="line"><a id="l00018" name="l00018"></a><span class="lineno">   18</span><span class="comment"> * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,</span></div>
<div class="line"><a id="l00019" name="l00019"></a><span class="lineno">   19</span><span class="comment"> * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE</span></div>
<div class="line"><a id="l00020" name="l00020"></a><span class="lineno">   20</span><span class="comment"> * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER</span></div>
<div class="line"><a id="l00021" name="l00021"></a><span class="lineno">   21</span><span class="comment"> * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,</span></div>
<div class="line"><a id="l00022" name="l00022"></a><span class="lineno">   22</span><span class="comment"> * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN</span></div>
<div class="line"><a id="l00023" name="l00023"></a><span class="lineno">   23</span><span class="comment"> * THE SOFTWARE. */</span></div>
<div class="line"><a id="l00024" name="l00024"></a><span class="lineno">   24</span><span class="comment"></span> </div>
<div class="line"><a id="l00025" name="l00025"></a><span class="lineno">   25</span><span class="comment">/// @file</span></div>
<div class="line"><a id="l00026" name="l00026"></a><span class="lineno">   26</span><span class="comment"></span><span class="preprocessor">#pragma once</span></div>
<div class="line"><a id="l00027" name="l00027"></a><span class="lineno">   27</span> </div>
<div class="line"><a id="l00028" name="l00028"></a><span class="lineno">   28</span><span class="preprocessor">#include &quot;<a class="code" href="struc__fwd_8hpp.html">ipc/transport/struc/struc_fwd.hpp</a>&quot;</span></div>
<div class="line"><a id="l00029" name="l00029"></a><span class="lineno">   29</span> </div>
<div class="line"><a id="l00030" name="l00030"></a><span class="lineno">   30</span><span class="keyword">namespace </span><a class="code hl_namespace" href="namespaceipc_1_1transport_1_1struc.html">ipc::transport::struc</a></div>
<div class="line"><a id="l00031" name="l00031"></a><span class="lineno">   31</span>{</div>
<div class="line"><a id="l00032" name="l00032"></a><span class="lineno">   32</span> </div>
<div class="line"><a id="l00033" name="l00033"></a><span class="lineno">   33</span><span class="comment">// Types.</span></div>
<div class="line"><a id="l00034" name="l00034"></a><span class="lineno">   34</span><span class="comment"></span> </div>
<div class="line"><a id="l00035" name="l00035"></a><span class="lineno">   35</span><span class="comment">/// `Channel` base that contains non-parameterized `public` items such as tag types and constants.</span></div>
<div class="line"><a id="l00036" name="l00036"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1struc_1_1Channel__base.html">   36</a></span><span class="comment"></span><span class="keyword">class </span><a class="code hl_class" href="classipc_1_1transport_1_1struc_1_1Channel__base.html">Channel_base</a></div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno">   37</span>{</div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno">   38</span><span class="keyword">public</span>:</div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno">   39</span>  <span class="comment">// Types.</span></div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno">   40</span><span class="comment"></span> </div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno">   41</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00042" name="l00042"></a><span class="lineno">   42</span><span class="comment">   * Clarifying short-hand for outgoing-message IDs.  This is public for logging/reporting use only</span></div>
<div class="line"><a id="l00043" name="l00043"></a><span class="lineno">   43</span><span class="comment">   * (see set_remote_unexpected_response_handler()) as of this writing.</span></div>
<div class="line"><a id="l00044" name="l00044"></a><span class="lineno">   44</span><span class="comment">   */</span></div>
<div class="line"><a id="l00045" name="l00045"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1struc_1_1Channel__base.html#adcf24fa51747ed83c4b6427fbf44fecf">   45</a></span>  <span class="keyword">using </span><a class="code hl_typedef" href="classipc_1_1transport_1_1struc_1_1Channel__base.html#adcf24fa51747ed83c4b6427fbf44fecf">msg_id_out_t</a> = <a class="code hl_typedef" href="namespaceipc_1_1transport_1_1struc.html#af7f35fc7588d97a838274fa25700ead9">msg_id_t</a>;</div>
<div class="line"><a id="l00046" name="l00046"></a><span class="lineno">   46</span><span class="comment"></span> </div>
<div class="line"><a id="l00047" name="l00047"></a><span class="lineno">   47</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00048" name="l00048"></a><span class="lineno">   48</span><span class="comment">   * Tag type for ctor selection: Backing memory for serialization comes from fixed-size segment allocation(s) from</span></div>
<div class="line"><a id="l00049" name="l00049"></a><span class="lineno">   49</span><span class="comment">   * regular heap (`malloc()`); and similarly for deserialization.  Therefore the serialization is copied</span></div>
<div class="line"><a id="l00050" name="l00050"></a><span class="lineno">   50</span><span class="comment">   * into the Channel::Owned_channel transport in the Channel::send() invoker process;</span></div>
<div class="line"><a id="l00051" name="l00051"></a><span class="lineno">   51</span><span class="comment">   * then copied out of there by the opposing (receiving) process.  I.e., this mode is *not* zero-copy, in</span></div>
<div class="line"><a id="l00052" name="l00052"></a><span class="lineno">   52</span><span class="comment">   * both directions.</span></div>
<div class="line"><a id="l00053" name="l00053"></a><span class="lineno">   53</span><span class="comment">   *</span></div>
<div class="line"><a id="l00054" name="l00054"></a><span class="lineno">   54</span><span class="comment">   * More specifically: Heap_fixed_builder and Heap_reader are the serialization engines used.</span></div>
<div class="line"><a id="l00055" name="l00055"></a><span class="lineno">   55</span><span class="comment">   *</span></div>
<div class="line"><a id="l00056" name="l00056"></a><span class="lineno">   56</span><span class="comment">   * For concision, and to compile successfully, use the struc::Channel alias class template:</span></div>
<div class="line"><a id="l00057" name="l00057"></a><span class="lineno">   57</span><span class="comment">   * #Channel_via_heap.</span></div>
<div class="line"><a id="l00058" name="l00058"></a><span class="lineno">   58</span><span class="comment">   *</span></div>
<div class="line"><a id="l00059" name="l00059"></a><span class="lineno">   59</span><span class="comment">   * ### Relative benefits/limitations (versus SHM-based `Serializa_via_*_shm`s) ###</span></div>
<div class="line"><a id="l00060" name="l00060"></a><span class="lineno">   60</span><span class="comment">   * These are discussed in some detail in Heap_fixed_builder doc header.  Short version:</span></div>
<div class="line"><a id="l00061" name="l00061"></a><span class="lineno">   61</span><span class="comment">   * Pros:</span></div>
<div class="line"><a id="l00062" name="l00062"></a><span class="lineno">   62</span><span class="comment">   *   - It&#39;s simple internally and externally, and cleanup is 100% guaranteed (no kernel-persistent resources</span></div>
<div class="line"><a id="l00063" name="l00063"></a><span class="lineno">   63</span><span class="comment">   *     are involved in serialization of structured messages).</span></div>
<div class="line"><a id="l00064" name="l00064"></a><span class="lineno">   64</span><span class="comment">   *     - In terms of simplicity specifically: it is not required to operate within ipc::session at all;</span></div>
<div class="line"><a id="l00065" name="l00065"></a><span class="lineno">   65</span><span class="comment">   *       whereas `Serializa_via_*_shm` are so required.</span></div>
<div class="line"><a id="l00066" name="l00066"></a><span class="lineno">   66</span><span class="comment">   *       - Subtlety: One *can* operate the SHM-based builders without ipc::session.  To do so you&#39;ll have to</span></div>
<div class="line"><a id="l00067" name="l00067"></a><span class="lineno">   67</span><span class="comment">   *         use the struc::Channel ctor form wherein you provide your own builder and reader engines</span></div>
<div class="line"><a id="l00068" name="l00068"></a><span class="lineno">   68</span><span class="comment">   *         which you&#39;ll need to first create manually.  One cannot do so with Serialize_via_heap ctor form,</span></div>
<div class="line"><a id="l00069" name="l00069"></a><span class="lineno">   69</span><span class="comment">   *         however, which is intended for easiest possible struc::Channel setup.</span></div>
<div class="line"><a id="l00070" name="l00070"></a><span class="lineno">   70</span><span class="comment">   *</span></div>
<div class="line"><a id="l00071" name="l00071"></a><span class="lineno">   71</span><span class="comment">   * Cons:</span></div>
<div class="line"><a id="l00072" name="l00072"></a><span class="lineno">   72</span><span class="comment">   *   - It&#39;s not zero-copy.  A linear-time copy is involved on each side of a transmitted message&#39;s processing.</span></div>
<div class="line"><a id="l00073" name="l00073"></a><span class="lineno">   73</span><span class="comment">   *   - If a leaf is too large to fit into the underlying `Owned_channel` pipe, the transmission will fail,</span></div>
<div class="line"><a id="l00074" name="l00074"></a><span class="lineno">   74</span><span class="comment">   *     and the struc::Channel will be hosed.  I.e., it places limits on what can be transmitted, and the</span></div>
<div class="line"><a id="l00075" name="l00075"></a><span class="lineno">   75</span><span class="comment">   *     exact nature of these limits is not 100% exact/predictable.</span></div>
<div class="line"><a id="l00076" name="l00076"></a><span class="lineno">   76</span><span class="comment">   */</span></div>
<div class="line"><a id="l00077" name="l00077"></a><span class="lineno"><a class="line" href="structipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__heap.html">   77</a></span>  <span class="keyword">struct </span><a class="code hl_struct" href="structipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__heap.html">Serialize_via_heap</a> {};</div>
<div class="line"><a id="l00078" name="l00078"></a><span class="lineno">   78</span><span class="comment"></span> </div>
<div class="line"><a id="l00079" name="l00079"></a><span class="lineno">   79</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00080" name="l00080"></a><span class="lineno">   80</span><span class="comment">   * Tag type for ctor selection: Backing RAM for serialization comes from a given session::Session&#39;s SHM arena</span></div>
<div class="line"><a id="l00081" name="l00081"></a><span class="lineno">   81</span><span class="comment">   * (of per-session scope) via exponential-growing-size segment allocation(s).  Subsequent deserialization in the</span></div>
<div class="line"><a id="l00082" name="l00082"></a><span class="lineno">   82</span><span class="comment">   * opposing process occurs from directly within the same backing RAM area(s).  Therefore the serialization</span></div>
<div class="line"><a id="l00083" name="l00083"></a><span class="lineno">   83</span><span class="comment">   * is *never* copied, period; only a short handle is internally copied into and out of the `Owned_channel` transport.</span></div>
<div class="line"><a id="l00084" name="l00084"></a><span class="lineno">   84</span><span class="comment">   * Conversely, the opposing process does the same as the sender, and we do the converse as the receiver.</span></div>
<div class="line"><a id="l00085" name="l00085"></a><span class="lineno">   85</span><span class="comment">   * I.e., this mode *is* zero-copy, in both directions.  Serialize_via_session_shm is usable only within the</span></div>
<div class="line"><a id="l00086" name="l00086"></a><span class="lineno">   86</span><span class="comment">   * ipc::session framework; if you are operating outside it then use the struc::Channel ctor form wherein the</span></div>
<div class="line"><a id="l00087" name="l00087"></a><span class="lineno">   87</span><span class="comment">   * builder/reader engines are supplied as args.</span></div>
<div class="line"><a id="l00088" name="l00088"></a><span class="lineno">   88</span><span class="comment">   *</span></div>
<div class="line"><a id="l00089" name="l00089"></a><span class="lineno">   89</span><span class="comment">   * More specifically, as of this writing: If the `Session` type in tag-form struc::Channel ctor is</span></div>
<div class="line"><a id="l00090" name="l00090"></a><span class="lineno">   90</span><span class="comment">   * session::shm::classic::Server_session or session::shm::classic::Client_session,</span></div>
<div class="line"><a id="l00091" name="l00091"></a><span class="lineno">   91</span><span class="comment">   * then shm::classic::Builder and shm::classic::Reader are the [de]serialization engines used.  If the</span></div>
<div class="line"><a id="l00092" name="l00092"></a><span class="lineno">   92</span><span class="comment">   * `Session` type in tag-form struc::Channel ctor is session::shm::arena_lend::jemalloc::Server_session</span></div>
<div class="line"><a id="l00093" name="l00093"></a><span class="lineno">   93</span><span class="comment">   * or session::shm::arena_lend::jemalloc::Client_session, then shm::arena_lend::jemalloc::Builder and</span></div>
<div class="line"><a id="l00094" name="l00094"></a><span class="lineno">   94</span><span class="comment">   * shm::arena_lend::jemalloc::Reader are the [de]serialization engines used.  The source arena for our serialization</span></div>
<div class="line"><a id="l00095" name="l00095"></a><span class="lineno">   95</span><span class="comment">   * (message building) comes from the `Session` impl supplied nearby in the ctor call; specifically its</span></div>
<div class="line"><a id="l00096" name="l00096"></a><span class="lineno">   96</span><span class="comment">   * `.session_shm()` arena.</span></div>
<div class="line"><a id="l00097" name="l00097"></a><span class="lineno">   97</span><span class="comment">   *</span></div>
<div class="line"><a id="l00098" name="l00098"></a><span class="lineno">   98</span><span class="comment">   * For concision, and to compile successfully, use the struc::Channel alias class template:</span></div>
<div class="line"><a id="l00099" name="l00099"></a><span class="lineno">   99</span><span class="comment">   * shm::classic::Channel or shm::arena_lend::jemalloc::Channel.</span></div>
<div class="line"><a id="l00100" name="l00100"></a><span class="lineno">  100</span><span class="comment">   *</span></div>
<div class="line"><a id="l00101" name="l00101"></a><span class="lineno">  101</span><span class="comment">   * Relative benefits/limitations</span></div>
<div class="line"><a id="l00102" name="l00102"></a><span class="lineno">  102</span><span class="comment">   * -----------------------------</span></div>
<div class="line"><a id="l00103" name="l00103"></a><span class="lineno">  103</span><span class="comment">   * ### As compared to Serialize_via_heap ###</span></div>
<div class="line"><a id="l00104" name="l00104"></a><span class="lineno">  104</span><span class="comment">   * Essentially they are the inverse of those of Serialize_via_heap above.</span></div>
<div class="line"><a id="l00105" name="l00105"></a><span class="lineno">  105</span><span class="comment">   *</span></div>
<div class="line"><a id="l00106" name="l00106"></a><span class="lineno">  106</span><span class="comment">   * ### shm::classic::Channel versus shm::arena_lend::jemalloc::Channel ###</span></div>
<div class="line"><a id="l00107" name="l00107"></a><span class="lineno">  107</span><span class="comment">   * The relative merits of the two SHM providers (SHM-classic versus SHM-jemalloc) in ipc::shm are discussed within</span></div>
<div class="line"><a id="l00108" name="l00108"></a><span class="lineno">  108</span><span class="comment">   * that namespace&#39;s docs.  Short version:</span></div>
<div class="line"><a id="l00109" name="l00109"></a><span class="lineno">  109</span><span class="comment">   *   - SHM-jemalloc is intended for safety (due to its asymmetrical internally-IPC-using nature) and efficiency of</span></div>
<div class="line"><a id="l00110" name="l00110"></a><span class="lineno">  110</span><span class="comment">   *     allocation (jemalloc is an industry-strength `malloc()` impl, which we&#39;ve adapted to SHM use; whereas</span></div>
<div class="line"><a id="l00111" name="l00111"></a><span class="lineno">  111</span><span class="comment">   *     SHM-classic uses boost.ipc&#39;s relatively rudimentary default allocation algorithm (e.g., it does not do thread</span></div>
<div class="line"><a id="l00112" name="l00112"></a><span class="lineno">  112</span><span class="comment">   *     caching)).</span></div>
<div class="line"><a id="l00113" name="l00113"></a><span class="lineno">  113</span><span class="comment">   */</span></div>
<div class="line"><a id="l00114" name="l00114"></a><span class="lineno"><a class="line" href="structipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__session__shm.html">  114</a></span>  <span class="keyword">struct </span><a class="code hl_struct" href="structipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__session__shm.html">Serialize_via_session_shm</a> {};</div>
<div class="line"><a id="l00115" name="l00115"></a><span class="lineno">  115</span><span class="comment"></span> </div>
<div class="line"><a id="l00116" name="l00116"></a><span class="lineno">  116</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00117" name="l00117"></a><span class="lineno">  117</span><span class="comment">   * Similar to Serialize_via_session_shm but assumes per-app-scope SHM-arena (as opposed to</span></div>
<div class="line"><a id="l00118" name="l00118"></a><span class="lineno">  118</span><span class="comment">   * per-session-scope) at compile time.  More specifically: The source arena for our serialization comes from the</span></div>
<div class="line"><a id="l00119" name="l00119"></a><span class="lineno">  119</span><span class="comment">   * `Session` impl supplied nearby in the ctor call; specifically its `.app_shm()` arena.  As for deserialization</span></div>
<div class="line"><a id="l00120" name="l00120"></a><span class="lineno">  120</span><span class="comment">   * on our end: we will be able to handle any objects sent from the other side, period.</span></div>
<div class="line"><a id="l00121" name="l00121"></a><span class="lineno">  121</span><span class="comment">   *</span></div>
<div class="line"><a id="l00122" name="l00122"></a><span class="lineno">  122</span><span class="comment">   * `Session` must be specifically *not* of the `&quot;ipc::session::shm::arena_lend::*::Server_session&quot;` variety;</span></div>
<div class="line"><a id="l00123" name="l00123"></a><span class="lineno">  123</span><span class="comment">   * `&quot;ipc::session::shm::arena_lend::*::Client_session&quot;` cannot be used (any attempt</span></div>
<div class="line"><a id="l00124" name="l00124"></a><span class="lineno">  124</span><span class="comment">   * will not compile).  This is because the latter lacks `.app_shm()` due to the nature of arena-lending</span></div>
<div class="line"><a id="l00125" name="l00125"></a><span class="lineno">  125</span><span class="comment">   * SHM providers, where each process allocates from an arena it maintains for itself (and from which</span></div>
<div class="line"><a id="l00126" name="l00126"></a><span class="lineno">  126</span><span class="comment">   * the other process can only borrow objects).  Some more notes on this are below in this doc header.</span></div>
<div class="line"><a id="l00127" name="l00127"></a><span class="lineno">  127</span><span class="comment">   *</span></div>
<div class="line"><a id="l00128" name="l00128"></a><span class="lineno">  128</span><span class="comment">   * For concision, and to compile successfully, use the struc::Channel alias class template:</span></div>
<div class="line"><a id="l00129" name="l00129"></a><span class="lineno">  129</span><span class="comment">   * shm::classic::Channel or shm::arena_lend::jemalloc::Channel.</span></div>
<div class="line"><a id="l00130" name="l00130"></a><span class="lineno">  130</span><span class="comment">   *</span></div>
<div class="line"><a id="l00131" name="l00131"></a><span class="lineno">  131</span><span class="comment">   * Relative benefits/limitations</span></div>
<div class="line"><a id="l00132" name="l00132"></a><span class="lineno">  132</span><span class="comment">   * -----------------------------</span></div>
<div class="line"><a id="l00133" name="l00133"></a><span class="lineno">  133</span><span class="comment">   * ### As compared to Serialize_via_heap ###</span></div>
<div class="line"><a id="l00134" name="l00134"></a><span class="lineno">  134</span><span class="comment">   * Essentially they are the inverse of those of Serialize_via_heap above.</span></div>
<div class="line"><a id="l00135" name="l00135"></a><span class="lineno">  135</span><span class="comment">   *</span></div>
<div class="line"><a id="l00136" name="l00136"></a><span class="lineno">  136</span><span class="comment">   * ### shm::classic::Channel versus shm::arena_lend::jemalloc::Channel ###</span></div>
<div class="line"><a id="l00137" name="l00137"></a><span class="lineno">  137</span><span class="comment">   * See Serialize_via_session_shm.</span></div>
<div class="line"><a id="l00138" name="l00138"></a><span class="lineno">  138</span><span class="comment">   *</span></div>
<div class="line"><a id="l00139" name="l00139"></a><span class="lineno">  139</span><span class="comment">   * In addition there is a *possibly* crucial difference in capabilities, depending on one&#39;s app needs</span></div>
<div class="line"><a id="l00140" name="l00140"></a><span class="lineno">  140</span><span class="comment">   * (it is mentioned above in this doc header):</span></div>
<div class="line"><a id="l00141" name="l00141"></a><span class="lineno">  141</span><span class="comment">   *   - With SHM-jemalloc (via shm::arena_lend::jemalloc::Channel), it is *not* possible</span></div>
<div class="line"><a id="l00142" name="l00142"></a><span class="lineno">  142</span><span class="comment">   *     to use this per-app-scope mode on the client side; only per-session scope is available (this is</span></div>
<div class="line"><a id="l00143" name="l00143"></a><span class="lineno">  143</span><span class="comment">   *     a consequence of its asymmetrical, safety-oriented design as of this writing).</span></div>
<div class="line"><a id="l00144" name="l00144"></a><span class="lineno">  144</span><span class="comment">   *     On the `Server_session` end it is possible to create out-messages in either scope however.</span></div>
<div class="line"><a id="l00145" name="l00145"></a><span class="lineno">  145</span><span class="comment">   *     - An attempt to use this per-app-scope mode with a `session::shm::arena_lend::jemalloc::Client_session`</span></div>
<div class="line"><a id="l00146" name="l00146"></a><span class="lineno">  146</span><span class="comment">   *       will be caught at compile time (it... won&#39;t compile).</span></div>
<div class="line"><a id="l00147" name="l00147"></a><span class="lineno">  147</span><span class="comment">   *     - Specifically, then, with SHM-jemalloc, in session-server use either Serialize_via_app_shm or</span></div>
<div class="line"><a id="l00148" name="l00148"></a><span class="lineno">  148</span><span class="comment">   *       Serialize_via_session_shm; in the opposing session-client use the latter only.  Deserialization will work</span></div>
<div class="line"><a id="l00149" name="l00149"></a><span class="lineno">  149</span><span class="comment">   *       on both sides; but serialization (building/sending) will work only for session-scope resources</span></div>
<div class="line"><a id="l00150" name="l00150"></a><span class="lineno">  150</span><span class="comment">   *       (again, attempt to do otherwise will not compile).</span></div>
<div class="line"><a id="l00151" name="l00151"></a><span class="lineno">  151</span><span class="comment">   */</span></div>
<div class="line"><a id="l00152" name="l00152"></a><span class="lineno"><a class="line" href="structipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__app__shm.html">  152</a></span>  <span class="keyword">struct </span><a class="code hl_struct" href="structipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__app__shm.html">Serialize_via_app_shm</a> {};</div>
<div class="line"><a id="l00153" name="l00153"></a><span class="lineno">  153</span> </div>
<div class="line"><a id="l00154" name="l00154"></a><span class="lineno">  154</span>  <span class="comment">// Constants.</span></div>
<div class="line"><a id="l00155" name="l00155"></a><span class="lineno">  155</span><span class="comment"></span> </div>
<div class="line"><a id="l00156" name="l00156"></a><span class="lineno">  156</span><span class="comment">  /// The sole value of the tag type Serialize_via_heap.</span></div>
<div class="line"><a id="l00157" name="l00157"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1struc_1_1Channel__base.html#ab0eb05b5fb52364c99868a8535aaf26e">  157</a></span><span class="comment"></span>  <span class="keyword">static</span> <span class="keyword">constexpr</span> <a class="code hl_struct" href="structipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__heap.html">Serialize_via_heap</a> <a class="code hl_variable" href="classipc_1_1transport_1_1struc_1_1Channel__base.html#ab0eb05b5fb52364c99868a8535aaf26e">S_SERIALIZE_VIA_HEAP</a> = {};</div>
<div class="line"><a id="l00158" name="l00158"></a><span class="lineno">  158</span><span class="comment"></span> </div>
<div class="line"><a id="l00159" name="l00159"></a><span class="lineno">  159</span><span class="comment">  /// The sole value of the tag type Serialize_via_session_shm.</span></div>
<div class="line"><a id="l00160" name="l00160"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1struc_1_1Channel__base.html#a9bdb94c1ba4fac92fbbd0f843e8525ba">  160</a></span><span class="comment"></span>  <span class="keyword">static</span> <span class="keyword">constexpr</span> <a class="code hl_struct" href="structipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__session__shm.html">Serialize_via_session_shm</a> <a class="code hl_variable" href="classipc_1_1transport_1_1struc_1_1Channel__base.html#a9bdb94c1ba4fac92fbbd0f843e8525ba">S_SERIALIZE_VIA_SESSION_SHM</a> = {};</div>
<div class="line"><a id="l00161" name="l00161"></a><span class="lineno">  161</span><span class="comment"></span> </div>
<div class="line"><a id="l00162" name="l00162"></a><span class="lineno">  162</span><span class="comment">  /// The sole value of the tag type Serialize_via_app_shm.</span></div>
<div class="line"><a id="l00163" name="l00163"></a><span class="lineno"><a class="line" href="classipc_1_1transport_1_1struc_1_1Channel__base.html#af732121649271d1368a2fb637917ce7b">  163</a></span><span class="comment"></span>  <span class="keyword">static</span> <span class="keyword">constexpr</span> <a class="code hl_struct" href="structipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__app__shm.html">Serialize_via_app_shm</a> <a class="code hl_variable" href="classipc_1_1transport_1_1struc_1_1Channel__base.html#af732121649271d1368a2fb637917ce7b">S_SERIALIZE_VIA_APP_SHM</a> = {};</div>
<div class="line"><a id="l00164" name="l00164"></a><span class="lineno">  164</span>}; <span class="comment">// class Channel_base</span></div>
<div class="line"><a id="l00165" name="l00165"></a><span class="lineno">  165</span> </div>
<div class="line"><a id="l00166" name="l00166"></a><span class="lineno">  166</span>} <span class="comment">// namespace ipc::transport::struc</span></div>
<div class="ttc" id="aclassipc_1_1transport_1_1struc_1_1Channel__base_html"><div class="ttname"><a href="classipc_1_1transport_1_1struc_1_1Channel__base.html">ipc::transport::struc::Channel_base</a></div><div class="ttdoc">Channel base that contains non-parameterized public items such as tag types and constants.</div><div class="ttdef"><b>Definition:</b> <a href="channel__base_8hpp_source.html#l00036">channel_base.hpp:37</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1struc_1_1Channel__base_html_a9bdb94c1ba4fac92fbbd0f843e8525ba"><div class="ttname"><a href="classipc_1_1transport_1_1struc_1_1Channel__base.html#a9bdb94c1ba4fac92fbbd0f843e8525ba">ipc::transport::struc::Channel_base::S_SERIALIZE_VIA_SESSION_SHM</a></div><div class="ttdeci">static constexpr Serialize_via_session_shm S_SERIALIZE_VIA_SESSION_SHM</div><div class="ttdoc">The sole value of the tag type Serialize_via_session_shm.</div><div class="ttdef"><b>Definition:</b> <a href="channel__base_8hpp_source.html#l00160">channel_base.hpp:160</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1struc_1_1Channel__base_html_ab0eb05b5fb52364c99868a8535aaf26e"><div class="ttname"><a href="classipc_1_1transport_1_1struc_1_1Channel__base.html#ab0eb05b5fb52364c99868a8535aaf26e">ipc::transport::struc::Channel_base::S_SERIALIZE_VIA_HEAP</a></div><div class="ttdeci">static constexpr Serialize_via_heap S_SERIALIZE_VIA_HEAP</div><div class="ttdoc">The sole value of the tag type Serialize_via_heap.</div><div class="ttdef"><b>Definition:</b> <a href="channel__base_8hpp_source.html#l00157">channel_base.hpp:157</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1struc_1_1Channel__base_html_adcf24fa51747ed83c4b6427fbf44fecf"><div class="ttname"><a href="classipc_1_1transport_1_1struc_1_1Channel__base.html#adcf24fa51747ed83c4b6427fbf44fecf">ipc::transport::struc::Channel_base::msg_id_out_t</a></div><div class="ttdeci">msg_id_t msg_id_out_t</div><div class="ttdoc">Clarifying short-hand for outgoing-message IDs.</div><div class="ttdef"><b>Definition:</b> <a href="channel__base_8hpp_source.html#l00045">channel_base.hpp:45</a></div></div>
<div class="ttc" id="aclassipc_1_1transport_1_1struc_1_1Channel__base_html_af732121649271d1368a2fb637917ce7b"><div class="ttname"><a href="classipc_1_1transport_1_1struc_1_1Channel__base.html#af732121649271d1368a2fb637917ce7b">ipc::transport::struc::Channel_base::S_SERIALIZE_VIA_APP_SHM</a></div><div class="ttdeci">static constexpr Serialize_via_app_shm S_SERIALIZE_VIA_APP_SHM</div><div class="ttdoc">The sole value of the tag type Serialize_via_app_shm.</div><div class="ttdef"><b>Definition:</b> <a href="channel__base_8hpp_source.html#l00163">channel_base.hpp:163</a></div></div>
<div class="ttc" id="anamespaceipc_1_1transport_1_1struc_html"><div class="ttname"><a href="namespaceipc_1_1transport_1_1struc.html">ipc::transport::struc</a></div><div class="ttdoc">Sub-module of Flow-IPC module ipc::transport providing transmission of structured messages specifical...</div><div class="ttdef"><b>Definition:</b> <a href="ipc__transport__structured_2src_2ipc_2transport_2struc_2channel_8cpp_source.html#l00030">channel.cpp:31</a></div></div>
<div class="ttc" id="anamespaceipc_1_1transport_1_1struc_html_af7f35fc7588d97a838274fa25700ead9"><div class="ttname"><a href="namespaceipc_1_1transport_1_1struc.html#af7f35fc7588d97a838274fa25700ead9">ipc::transport::struc::msg_id_t</a></div><div class="ttdeci">uint64_t msg_id_t</div><div class="ttdoc">Message ID uniquely identifying outgoing message (Msg_out, among all other Msg_outs),...</div><div class="ttdef"><b>Definition:</b> <a href="struc__fwd_8hpp_source.html#l00145">struc_fwd.hpp:145</a></div></div>
<div class="ttc" id="astruc__fwd_8hpp_html"><div class="ttname"><a href="struc__fwd_8hpp.html">struc_fwd.hpp</a></div></div>
<div class="ttc" id="astructipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__app__shm_html"><div class="ttname"><a href="structipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__app__shm.html">ipc::transport::struc::Channel_base::Serialize_via_app_shm</a></div><div class="ttdoc">Similar to Serialize_via_session_shm but assumes per-app-scope SHM-arena (as opposed to per-session-s...</div><div class="ttdef"><b>Definition:</b> <a href="channel__base_8hpp_source.html#l00152">channel_base.hpp:152</a></div></div>
<div class="ttc" id="astructipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__heap_html"><div class="ttname"><a href="structipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__heap.html">ipc::transport::struc::Channel_base::Serialize_via_heap</a></div><div class="ttdoc">Tag type for ctor selection: Backing memory for serialization comes from fixed-size segment allocatio...</div><div class="ttdef"><b>Definition:</b> <a href="channel__base_8hpp_source.html#l00077">channel_base.hpp:77</a></div></div>
<div class="ttc" id="astructipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__session__shm_html"><div class="ttname"><a href="structipc_1_1transport_1_1struc_1_1Channel__base_1_1Serialize__via__session__shm.html">ipc::transport::struc::Channel_base::Serialize_via_session_shm</a></div><div class="ttdoc">Tag type for ctor selection: Backing RAM for serialization comes from a given session::Session's SHM ...</div><div class="ttdef"><b>Definition:</b> <a href="channel__base_8hpp_source.html#l00114">channel_base.hpp:114</a></div></div>
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